over-tanned

A condition in which the grain and flesh sides of
a hide or skin have received an excess of tannin
in relation to the interior, or corium, of the
skin. It results from the grain and flesh sides
being exposed to a strong tannin liquor and
becoming over-tanned while the corium has had
insufficient exposure. The problem can be avoided
by using weaker liquors initially, and building to
stronger solutions as tanning progresses. Over
tanning produces a hard, thin leather, often with
a cracky, distorted (drawn) grain. See also: CASE-HARDENING . (306 )